Treatment of materials containing tungsten compounds



advantages result:

Patented Dec. 26, 1950 TREATMENT OF MATERIALS CONTAINING TUNGSTENCONIPOUNDS Kuo Ching Li and Carl Marion Dice, Glen Cove,

N. Y., assignors to Wah Chang Trading Corporation, New York, N. Y., a.corporation of New York No Drawing. Application August 24, 1948, SerialNo. 45,982

7 Claims. (Cl. 75-122) This invention relates to the treatment ofmaterials containing tungsten oxide, such as ores, concentrates or theresidual products of the beneficiation or treatment of ores or othersubstances in which tungsten oxides appear. The broad object of theinvention is the production of relatively pure tungsten bearingsubstances, of the class consisting of tungsten carbide orferrotungsten, from such materials.

More specific objects include the provision of commercial processes bywhich such tungsten containing products may be produced from complexmaterials which contain, in addition to tungsten oxide, such elements,or compounds thereof, as tin, copper, arsenic, sulphur, phosphorus,lead, bismuth and antimony.

A further obiect of the invention is a comparativel low cost process ofwinning relatively pure tungsten products and tin values from oxidictungsten ores containing substantial amounts of tin values.

The specific objects above indicated have not 'previously been achievedin commercial operation by processes involving the direct reduction oftungsten from tungsten oxide bearing materials. Such processes havealways required very high temperatures for operation and whatevermetallic values as are present in the tungsten oxide bearing materialhave been found in the final tungsten bearing product. The presentinvention provides a method of direct reduction which does not requireas high an operating temperature and which prevents foreign metallicvalues, from entering in any substantial amount into the tungstencarbide or ferrotungsten which is the end product desired. Otheradvantages of the invention will be noted in, or are apparent from, thefollowing description.

It is the gist of the present invention that the tungsten oxide isreduced and the resulting carbide or ferrotungsten formed in thepresence of, or in some cases, during the simultaneous formation of, analloy of iron and tin. We have found that when this condition isachieved two major first, any metallic values present in the tungstenoxide bearing material, which would otherwise be found in the resultingcarbide or ferrotungsten, are preferentially taken up in the iron-tinalloy, and, second, the reduction process proceeds eificiently at lowertemperatures. Thus the invention can best be described byinitiallyconsidering the product of such a reduction. This product isintermediate in nature and consists, when solidified, of a metallicmixture or alloy essentially composed of a tungsten carbide orferrotungsten component,

' or both, embedded in a matrix of iron-tin alloy which matrix containsmost, if not all, of the other metallic values present as impurities inthe tungsten oxide bearing material, the tung- 'sten component of thealloy being substantially free from metallic impurities. Essentiallythis product is but a source of a final high purity ferrotungsten ortungsten carbide, these materials being separable from the alloy bymethods hereinafter described. The amount of iron-tin alloy matrix whichappears in the solidified product of the methods of this invention neednot be great but should be substantial in the sense that it forms, byweight at least about ten per-cent by weight of the solidified alloy.

The methods of this invention may be performed by establishing a bath ofmolten irontin alloy and addin to this bath the tungsten oxide hearingare together with carbon suflicient to reduce the same under suchconditions of temperature and the like as will insure a satisfactoryreduction. However, tungsten ores as they occur in nature carrysubstantial tin values and some iron values, many tin ores carry sometungsten values and residues resulting from the beneficiation oftungsten ores often carry high tin values and iron values together withresidual tungsten values. Since these values may be simultaneouslyreduced by reaction with carbon the most economical commercial practiceof the principles of this invention utilizes as starting materials thecheaper tin and iron values available in such ores and residues. Thus byproper selection and blending of ores, concentrates and residues acharge can be formed in which all of the tin values and iron valuesnecessary to the production of the desired iron-tin alloy are availablein inexpensive form and are simultaneously reduced with the tungstenoxide to form the iron-tin alloy with which the resultant tungstencarbide or ferrotungsten also alloys and from which these tungstenbodies crystalize during' solidification. Thus in practice it may befound possible to blend tungsten ores and residues so as to form acharge containing all of the necessary tin values and at least some ofthe necessary iron values, depending upon whether the product finallydesired is ferrotungsten or tungsten carbide and this is the preferredway of forming the ion-tin alloy. Where deficiencies of tin values occura tin ore may be used to furnish the additional values. Wheredeficiencies in iron values occur scrap iron or iron ore may be used asa further iron source in the charge.

In any event whether the charge originally contains the necessary ironand tin values or whether the desired iron-tin alloy be preformed andbrought separately to the reduction operation it will be found thatreduction of the tungsten oxide bearing charge will proceed efiicimtlyand satisfactorily at temperatures as low as 2500 degrees Fahrenheit.

The carbon component of the charge may be furnished by any convenientsource of carbon such as coal or coke. The amount of carbon in thecharge should be at Last sufiicient to reduce the metallic values fromtheir compounds to metallic state. When only sufficient carbon ispresent to effect this reduction the product of the smelting operationwill contain the reduced tungsten values in the form of ferrotungsten.IncrLaSing amounts of carbon in the charge will cause the reducedtungsten values to increasingly appear in the form of tungsten carbide.When the carbon content is such as to provide sufficient carbon toreduce the metallic values of the charge from their compounds to themetallic state and, additionally, enough carban to convert all thetungsten thus reduced to tungsten carbide, the resulting product willcontain the tungsten values in the form of carbide usually to theexcluson ofa-nyssubstantial amount of ferrotungsten. Thus by control ofcarbon content of the charge the tungsten values may be recovered astungsten carbide or as ferrotung- .sten, both forms being usefulproducts in the art particularly when they are relatively pure. Thetungsten carbide referred to herein possibly include a small amount ofthe double iron tungsten carbide (FeiWzC) but, for reasons Which are notapparent, only the monotungsten can bide -(-WC:) is obtained in anyquantity by the practice of this invention. The direct winning of thetungsten in the form :of the moniocarbide WC is :a desirable feature ofthe invention.

was previously noted the desired iron-tin alloy maybe furnished to thereduction operation as such or may be. formed by reductionor smelting\of components of the charge which includes the tungsten oxide values.In any event the amount of tin available should, for best results be :soadjusted that the iron-tin alloy contain between about 15 to 55 percentby weight of tin. Lower amounts down to, Say, percent may be toleratedbut will result in unduly raisthe temperatures of operation. High-eramounts of tin appear to have no deleterious effect but are not helpful.With higher amount of tin a tin :rich phase appears which does not seemto add to the :emciency of the operation. The tin iron alloy should inany event contain at-leasta-bout 25 percent by weight of iron. Thuswhile the invention may be practiced with charges including tin valuesin amounts less than or more than that required to produce an iron-tinmatrix in the solidified smelted product containing between --about Yand 55 percent by weight of tin, the best commercial conditions ofoperation will be achieved when the smelting charged is adjusted in tincontent as aforesaid. Otherwise the exact composition of iron-tin alloymatrix obtained by the smelting process is of little importance. Thismatrix is essentially an irontin alloy but it contains as above notedall, .or almostall, of themetallic impurities which, otherwise, wouldappear as deleterious impurities in the ferrotungsten or tungstencarbide phases .of the solidified smelting :product.

The available iron content of the smelting charge may be variedconsiderably within the .scope of this invention. It is at onceapparent.

from the foregoing discussion, that enough icon must be present tosatisfy the requirements of the iron-tin matrix alloy if the alloy isnot preformed, and in the absence of suflicient carbon "to completelyconvert the tungsten to tungsten carbide, to form ferrotungsten with thetungsten values. This amount can be determined by simple trial and ithas been so determined in the practice of this investigation. It wouldappear, although this statement cannot be made with finality in anabsolute sense, that, in general. iron present :in amount greater thanthat required to fulfill the intermetallic compound FezW, with tungstcnnot converted to carbide, will alloy with the tin to form the matrixiron-tin alloy. At fleastapplication of this general principle, Whetheror not it is correct, combined with simple trial, allows readyadjustment of the iron content of the charge to produce the desiredresult of the methods of this invention. Where the tungsten aoxidematerials contain some reducible iron =values these are of courseavailable for the purposes of the process and may be supplemented byother available iron values either in a preformed iron-tin alloy or inthe form of reducible iron ore or in the form of scrap iron or insimilar form. V

The smelting-charge may be composed, in accordance with the principlesabove set forth, of various materials. If the tungsten oxide bearingmaterial does not have suflicient tin values the tin values may be addedseparately, preferably in the form of tin ore, concentrates or otherrelatively inexpensive sources of tin. The tungsten oxide bearingmaterial will often contain substantial amounts of iron values whichmay, as is necessary, be supplemented by additions to the charge ofreducible iron ore, scrap iron or the like. Calculations of the chargemust, of course, treat tin values in terms of available tin values atthe temperatures of operation. This can be readily accomplished byobserving the fume loss of t n values due to causes such as the sulphuror-chloridecontent of the-charge and the time and temperature of thesmelting operation. As much as 35% of the tin charged may be lost as.fume. Such loss however may be readily estimated and suflicientallowance made therefor. Where a carbide free, or substantially carbide.f-ree, tungsten product is desired thesmelting operation must .beconducted in carbon free containers unless allowance be made incalculating the or ginal charge for the presence-of such containers.Carbide free operation can usually be assured under such circumstancesby deliberate withholding of sufiicient available carbon to effectcomplete reduction of the metallic values. Such calculations as these,in order to achieve the principles of operations above outlined, are*within the skill of the art and are only noted here by way of example.

The smelting charge thus formed is placed in any convenient smeltingapparatus adapted to the smelting conditions and heated, in the presenceof slag forming elements, as above indicated, until reduction iscomplete. The resultant molten metallic product is separated from theslag and cooled. The cooled intermediate product maybe then, or later,treated to separate the tungsten component or components as such and torecover other metallic values in suitable :form.

In this second, or separation step, various methods may be used. Thesemethods may be usually preceded by crushing the iron-tin matrix iihflproduct is comparatively brittle.) or otherwise disintegrating orsubdividing, the metallic product into discrete particles. At this pointit may be advantageous to use known principles of magnetic separation toseparate the non-ma netic tungsten component, or components, from themagnetic iron-tin alloy which contains the other metallics reducedduring the smelting operation. In addition, or in lieu thereof, chemicalmethods of separation may be employed. Gravity or flotation separationmethods may likewise be used. The comparatively low melting range of theiron-tin matrix also afiords the possibility of re-heating the finalproduct to effect gravity separation of the higher melting pointconstituents.

While any of these indicated separation methods may be used singly or incombination, the preferred separation procedure, having due regard forthe desirability of obtaining a tungsten product of high purity and aneffectual recovery of other metallic values, is, in accordance with thisinvention, essentially a leaching process.

Thus in the preferred practice of the methods of this invention thesolidified metallic product of the smelting operation is mechanicallyreduced, as by crushing or pulverization, to discrete particles. Theseparticles are then leached in an aqueous solution containing chlorine.The chlorine may be furnished as such or as hydrochloric acid or gaseousHCl. Under these conditions the iron values, other than those of theferrotungsten, and the tin values are converted to their respectivesoluble chlorides. The tungsten component, ferrotungsten, tungstencarbide or both, remains as insoluble. Also present are insolubles inthe form of slimes which will usually contain some tungsten values andalso other metallic values as Well as non-metallic values.

Initial separation is made by decantation, filtration or otherwise, ofthe slimes and insoluble tungsten component from the leaching solution.The tun sten component is then separated from the slimes in anyconvenient manner, as by washing. The tin values may be precipitatedfrom the leaching liquor and either reused in the 4 smelting charge orotherwise converted by known methods to salable product.

The metallic impurities preferentially taken up in the iron-tin allowmatrix may, depending upon the chlorine concentration of the leachliquor and the metal in question, appear as metallics in the slimes oras soluble components in the leach liquor or both. In any case they may,if desired, be recovered in usuable form by known methods.

Some specific examples of preferred operation in accordance with theprinciples of this invention are as follows:

A. A smelting charge was formed by mixing 100 parts by weight oftungsten oxide bearing material with 10 parts by weight of scrap ironand 10 parts by weight of bituminous coal (ash approximately 12 percentb weight). The tungsten oxide bearing material was a mixture consistingof 66.7 percent by weight of a tungsten ore and 33.3 percent by weightof a residue. The ore and residue assayed as follows:

Per cent Ferrotungsten 86.65 -Slimes 7.89 Leach liquor 0.72 Slag 4.7

B. A charge was formed by mixing 100 parts by weight of tungsten oxidebearing material with 10 parts by weight of iron filings and 20 parts byweight of bituminous coal (about 12% ash). The tungsten oxide bearingmaterial was a mixture consisting of 66.7% by weight of ore and 33% byweight of a residue. The ore and residue assayed as follows:

VVO Sn Fe Cu AS S SiO C Ore 51. 27 3.3 15.45 .29 .23 .70 5.65 Residue 2.72 23. 84 ll. 70 09 13 60 12. 58 2. 68

The residue likewise contained 0.1 to 0.25% phosphorus. The charge wassmelted at about 2750 F. for 2 hours. The resulting metallic alloy wascooled crushed to pass a 14 mesh screen and leached with twice itsweight of 20 B. hydrochloric acid until visible reaction ceased. Theresidual tungsten component (consisting of both ferrotungsten andtungsten carbide) assayed as follows (all figures are percent by weight)W Sn Fe 0 P As Cu 83. 74 0. 4 7. 48 4. 49 0. O2 0. 04 trace contained85.61 percent of the available tungsten in the charge, the remainder ofthe tungsten values being found in the leach liquors and slimes.

The carbide thus produced contained only a trace of phosphorus and ofcopper, about 0.03 percent of arsenic, about 0.03 percent of tin andabout 0.01 percent of iron.

We have found it desirable to adjust the slag which, as is well knownformed in smelting processes and contains silicious and basic elementsof the ores, to insure that the slag present will have a relatively highsilicate degree.

Having thus described our invention, we claim:

1. The process of recovering tungsten from tungsten oxide bearingmaterials which includes reducing said oxide with carbon at temperaturesin excess of 2500 Fahrenheit in the presence of iron-tin alloycontaining between about 5 to 75 per cent by weight of tin, the totalamount of such alloy being such that it mom-poses at least about 10 percent 'of the total weight of said :aflloy and the tungsten lcontainingproduct ofzsaid seduction.

l he process of recovering tungsten from tungsten oxide bearingmaterials which includes rred-ucingsaid oxide with carbon attemperatures in excess of -2500 Farhenhei-t in the presence of iron-tinalloy containing between about to '55 per cent "by weight of tin, thetotal amount of such alloy being such that it composes at least about 10per centof the total weightof said alloy and the tungsten containingproduct of said .recluction.

3. The process of reducing tungsten -oxide rbearing material to obtaintungsten bearing sub- :stances of the class consisting of tungstencarbide and ferrotungsten which includes formin-ga charge containingtungsten oxide, available tin values and iron values and carbon, heatingsaid charge to temperatures in excess of 2500 Fahrenheit, cooling theresultant alloy and separating the tungsten bearing components thereof,the content of said charge beingso adjusted that said tin and ironvalues are sufficient in amount,

in respect of the tungsten and carbon content of the charge, to form inthe resultant alloy at least about 10 per cent by weight of=an iron-tinalloy matrix-containing between about '5 to 75 per cent of tin.

4. The process of reducing tungsten oxide bearing material to obtaintungsten bearing substances .of the class consisting of tungsten carbideand ferrotungsten which includes forming a charge containing tungstenoxide, available tin values and iron values and carbon, heating saidcharge to temperatures in excess of 2500 Fahrenheit, cooling theresultant alloy and separating the tungsten bearing components thereof,the content of said charge being so adjusted that said tin and ironvalues are sufiicient in amount, in respect of the tungsten and carboncontent of the charge, to form in the resultant alloy at least about 10per cent by weight of an iron-tin alloy matrix containing between about15 to 55 per cent of tin.

5. In a process of producing high purity tungsten containing substancesof the class consisting of tungsten carbide and ferrotu'ngs'ten and tinvalues from impure materials containing tungsten oxide and reducible tincompounds, forming a charge of said materials, carbon, and availableiron, the amount of tin compound and available iron being so adjusted asto furnish su'fficient tin and iron, in the eventual form of an iron-tinalloy containing 15 to 55 per cent by weight of tin, to compose at leastabout 10 per cent by weight of the total weight of said iron, said tinand said tungsten containing substance,

8 heating said charge to temperatures over about 2500 Fahrenheit toefiect reduction of reducible compounds therein, separating from theresultant metal alloy so formed said tungsten containing substances andseparating the tin values from the remainder.

'6. In a process of producing high purity tungsten carbide from impurematerials containing tungsten oxide and reducible tin compounds, forminga charge of said impure materials,available iron and at least sufficientcarbon to reduce the metallic compounds of said charge and to convertthe tungsten so reduced to WC, the amount of tin compound and availableiron in said charge being so adjusted as to furnish suflicient tin andiron, in the eventual form of an iron-tin alloy containing between about15 to 55 per cent by weight of tin, to compose at least about 10 percent by weight of the total weight of said tin, iron and tungstencarbide, heating said charge to temperatures in excess of about 2500Fahrenheit to efiect reduction of the reducible compounds therein, andseparating the tungsten carbide from the resultant alloy of "iron, tinand tungsten carbide.

7. In a process of producing high purity ferrotungsten from impurematerials containing tungsten oxide and reducible tin compounds, forminga charge of said impure materials, carbon in amount not greater thanthat required to reduce the reducible compounds of said charge, andavailable iron, the amount of tin compound and available iron in saidcharge being so adjusted that the tin content will be sufiicient with aportion of the iron, as an eventual iron-tin alloy containing betweenabout 15 to 55 per cent by weight of tin, to compose at least about 10per cent by weight of the total weight of said tin, iron andferrotungsten, and the iron content will be surficient to form saidiron-tin alloy and, in addition, to form ferrotungsten with thetungsten, heating said charge to temperatures in excess of about 2500Fahrenheit to effect reduction of reducible compounds therein, andseparating the tungsten carbide from the resultant alloy of iron, tinand ferrotungstcn.

.KUO CHING LI.

CARL MARION DICE.

REFERENCES CITED The following references are of record inthe file ofthis patent:

UNITED STATES PATENTS

1. THE PROCESS OF RECOVERING TUNGSTEN FROM TUNGSTEN OXIDE BEARINGMATERIALS WHICH INCLUDES REDUCING SAID OXIDE WITH CARBON AT TEMPERATURESIN EXCESS OF 2500* FAHRENHEIT IN THE PRESENCE OF IRON-TIN ALLOYCONTAINING BETWEN ABOUT 5 TO 75 PER CENT BY WEIGHT OF TIN, THE TOTALAMOUNT OF SUCH ALLOY BEING SUCH THAT IT COMPOSES AT LEAST ABOUT 10 PERCENT OF THE TOTAL WEIGHT OF SAID ALLOY AND THE TUNGSTEN CONTAININGPRODUCT OF SAID REDUCTION.